1. Field of the Invention
This invention relates to a mechanism for converting rotary motion into linear reciprocating motion, and more particulary to such a mechanism employing an endless chain disposed on spaced drive and driven sprockets, a slide member linearly movable on a guide rod mounted parallel to said chain, and a connecting rod pivotally coupled between said chain and said slide member.
2. Description of the Prior Art
There are a number of prior art mechanisms for converting rotary motion to linear reciprocating motion without repeatedly changing the rotational direction of the drive source, such as a crank arm system or the like. In a crank system, however, the reciprocation stroke is determined by the diameter of the drive disc or the length of the crank arm, which imposes a severe limitation where a desired stroke is needed and the space available for the mechanism will not accomodate a sufficiently large crank disc/arm.
In order to eliminate this drawback, a converting system as shown in FIG. 4 has been developed. In this Figure, reference numeral 51 designates a rotary drive pulley for a belt 52 coupled between the drive pulley and a driven pulley (not shown) spaced therefrom. A linear guide plate 53 and a slide member 54 mounted on the guide plate are disposed between the belt runs. A traveller 55 and a pinch rod 56 are pivotally mounted to the main slide member 54. The pinch rod 56 has arms 561, 562 and 563. Reference numerals 57 and 58 designate fixed stoppers. In this system, when the drive pully 51 rotates in the direction shown by the arrow, the belt 52 also moves in the same direction. The pinch rod 56 is biased in either one of two rotational positions by a stop pin 60 and a spring 59 mounted on the slide member 54. The latter moves toward the left, and when the arm 563 engages the stopper 57 at the left end, the pinch rod 56 cams in the stop pin 60 and rotates in a clockwise direction. This releases the upper belt run from the traveller 55 and the arm 562, and transfers the pinch engagement to the lower belt run, between the traveller 55 and the arm 561. Thus, the main slide member 54 moves in the reverse direction or toward the right. At the end of this stroke the arm 563 strikes the other stopper 58, the arm 562 engages the upper belt run again, and the main slide member 54 moves back in the left direction, thus converting the rotation of the drive pulley 51 to the linear reciprocation of the slide member 54.
Since this linear reciprocating motion is implemented by alternately switching the coupling between the pinch rod and the belt, however, the mechanism is relatively complicated, and high speed operation becomes quite rough and jerky. Further, since the pinch rod and traveller are disposed between the drive and driven pulleys the full belt run cannot be effectively utilized, and for a given linear stroke the space requirements are increased by more than twice the diameters of the pulleys. Also, the repeated belt pinching causes rapid wear and necessitates frequent belt replacement.